This book is recommended, but with a caveat. Like most books about international relations written by social scientists who tend to simplify things for the sake of providing an over-arching structure, this one is to be read with a measure of skepticism. For a detailed review (or two), check out the recent debate in Slate.com between the journalists Bill Emmott and Fareed Zakaria, who are, respectively, an editor of The Economist and a columnist for Newsweek. (You can search within Slate by typing out their names and the title of the exchange: "Debating the J-Curve".) Here's two quotes from their exchanges.
Emmott: "I found this a useful representation of what happens as institutions and regimes change and, certainly, a salutary warning against the view that democracy will grow as naturally as flowers in the spring. The book's main interest for me, however, lay not so much in the chart that gives it its title but in the fine and revealing case studies that Bremmer lays out to establish how complicated the political form of states really is. He outlines the situations in North Korea, Cuba, Iran, and China adeptly and looks also at countries, such as South Africa, that have made a successful transition to democracy; at others, such as India, where democracy has survived seemingly against the odds; and at Russia, where democracy has lately been foundering. The conclusion? That there is no clear rule that can guide us in judging which countries will move up the J curve and which will not. It all depends. Societies are fragile and complex organisms."
Zakaria: "he biggest real-world test of Bremmer's thesis is taking place right now in Asia. If he's right, India is a better long- and even medium-term bet than China. Is he correct? I look at China, which is doing so much economic and even social reform. Its strange free-market dictatorship is building world-class infrastructure--new schools, colleges, and universities; special economic zones; nuclear power plants--and is opening the economy and society to international trade. India, meanwhile, moves its reform process forward at a snail's pace, remaining in many ways well behind China, largely because it is a democracy and the government is busy subsidizing interest groups and voters. They're both doing fine, but China's economy is now three times the size of India's and grows about 2 percentage points faster. Will that change? I puzzle about this and am genuinely curious as to your response."
Political scientists may come up with elegant and even persuasive models such as this J-Curve. But in the long run, it's historians and their research that give the last words.